soilDB 2.7.6

All references to soilDB.env have been replaced with a function that returns that environment object (get_soilDB_env()); thanks to @MollicMeyer for identifying this as a problem in #277. This object used to be exported but was unintentionally omitted from NAMESPACE; this has been fixed.
fetchNASIS(lab=TRUE) bug fix related to many:1 relationships between lab samples and morphologic horizons with all-missing columns having logical datatype (#277)
Added get_SRI() and fetchSRI() functions for accessing USFS Region 6 Soil Resource Inventory information from https://ecoshare.info/; thanks to @joshualerickson for the contribution (#274)
fetchLDM() now sets the horizon designation metadata like other fetch* functions that return SoilProfileCollection objects (@dylanbeaudette)
mukey.wcs() fix spurious warnings occasionally given due to minor differences (rounding) of grid dimensions
{curl} has been moved from Suggests to Imports
simplfyFragmentData() alias for simplifyFragmentData() removed (@infotroph)

What's Changed

Full Changelog: 2.7.5...2.7.6